I’ve just read an excellent paper that succinctly, eloquently, and wisely summarised the current predicament of our highly interconnected, global, complex adaptive system (i.e., our environment).

If you are new to the discussions around state shifts, hysteresis, tipping points, and system collapse, there might be a lot in the new paper by Philip Garnett of the University of York that you could find intimidating (and not just because of the complexity of the concepts he discusses). If you are more up-to-date on these discussions, I highly recommend reading this paper for distilling some of the more pertinent questions.

The essence of the paper is that our global environment (Earth) is one giant, complex system made up of interacting sub-systems. We can think of these as a giant, interconnected network of nodes and connections (often called ‘edges’) between them. If you do ecological network theory, then you know what I’m talking about.

What’s particularly fascinating to me is that Philip Garnett is not an environmental scientist; in fact, he’s a a lecturer in Operations Management and Business Analytics (although he does have a background in genetics and biology) who specialises in complex systems theory. In fact, much of his paper uses socio-economic examples of system complexity and collapse, yet the applications to environmentalism in general, and to ecological integrity in particular, are spot on.

Climate change caused by industrialisation is modifying the structure and function of the Biosphere. As we uncork 2017, our team launches a monthly section on plant and animal responses to modern climate change in the Spanish magazine Quercus – with an English version in Conservation Bytes. The initiative is the outreach component of a research project on the expression and evolution of heat-shock proteins at the thermal limits of Iberian lizards (papers in progress), supported by the British Ecological Society and the Spanish Ministry of Economy, Industry and Competitiveness. The series will feature key papers (linking climate change and biodiversity) that have been published in the primary literature throughout the last decade. To set the scene, we start off putting the emphasis on how people perceive climate change.

“I would like to mention a cousin of mine, who is a Professor in Physics at the University of Seville – and asked about this matter [climate change], he stated: listen, I have gathered ten of the top scientists worldwide, and none has guaranteed what the weather will be like tomorrow in Seville, so how could anyone predict what is going to occur in the world 300 years ahead?”

Mariano Rajoy (Spanish President from 2011 to date) in a public speech on 22 October 2007

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Weather (studied by meteorology) behaves like a chaotic system, so a little variation in the atmosphere can trigger large meteorological changes in the short term that are hard to predict. On the contrary, climate (studied by climatology) is a measure of average conditions in the long term and thus far more predictable than weather. There is less uncertainty in a climate prediction for the next century than in a weather prediction for the next month. The incorrect statement made by the Spanish President reflects harsh misinformation and/or lack of environment-related knowledge among our politicians.

Climate has changed consistently from the onset of the Industrial Revolution. The IPCC’s latest report stablishes with 95 to 100% certainty (solid evidence and high consensus given published research) that greenhouse gases from human activities are the main drivers of global warming since the second half of the 20th Century (1,2). The IPCC also flags that current concentrations of those gases have no parallel in the last 800,000 years, and that climate predictions for the 21st Century vary mostly according to how we manage our greenhouse emissions (1,3). Read the rest of this entry »

In August I had the pleasure of visiting the National Centre for Biological Sciences in Bengaluru, India, and while there I was interviewed by Hari Sridhar of Current Conservation. I admit that I haven’t always fully appreciated the excellent conservation reporting done by Current Conservation, and now after having been interviewed by them, I’m becoming more aware of their value (and not just because I appear in their latest issue). I really encourage CB.com readers to check it out.

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In a paper published in the Proceedings of the National Academy of Sciences USA in 2014, Corey Bradshaw and Barry Brookargued that, given the current momentum of human population growth, no demographic “quick fixes” will be enough to change its trajectory in the near future. Therefore, environmental policy will be served better by prioritising measures such as technological and social innovation and reductions in consumption, while treating population reduction as a long-term goal. On his recent visit to Bengaluru, I spoke to Corey Bradshaw about the genesis of this study and its implications.

Hari Sridhar: You say “our models clearly demonstrate that the current momentum of the global human population precludes any demographic “quick fixes.” If that is the case, what do you suggest should be done instead?

Corey Bradshaw: I’ll back up a little bit and give you some of the context for writing the paper, which will sort of explain the title and that particular conclusion. Often when I gave public seminars, where I would talk about some environmental problem and future predictions of its worsening, some member of the audience would stand up at the end and say: “Well, the problem is humans. There are just too many of us. So all we need to do is focus on reducing the human population and we will fix all of these other problems.” That came up so often that I began to think: “Well, how quickly could we fix the overpopulation problem?”

Being, among other things, a population dynamics modeller, I decided I could model the human population just as well to look at that question. What would it take and how long for human population to start to decline, either from interventions or catastrophes? Human demographers don’t typically consider catastrophe scenarios when they project human populations. It’s instead done under very strict policy criteria, typically under the expected status quo, with some slight variation in things like family planning and structural change, you know, things like age structure. But we decided to try out more extreme scenarios as well to address that question. So first we said “let’s just see what happens when we only adjust fertility”. We did that and the population trajectory was more or less insensitive.

Then we said “let’s see what happens if we impose mass mortality events of various types — a third world war, pandemics, nuclear warfare” — and still the population was fairly resistant, even to these big changes. What we took away from these results was this: yes, population size must be addressed and we should have started looking into this seriously, probably post World War 2 when we were just under two billion people. We need to address overpopulation, but it’s not going to be something that can be fixed suddenly or be reduced anytime in the next few decades. It’s a century-scale issue. Should we be aiming to reduce the total human population? Yes. Should we be encouraging fertility reduction and family planning? Yes. It’s just that these will have positive outcomes at the century scale. Now most of our environmental problems are not things that we can ignore for a century. They have to be dealt with now. So our argument basically was that if we can’t address the human population problem, in the sense of reducing its size quickly, then we need to turn our attention to more immediate fixes, such as addressing consumption and various environmental mitigation policies. That was our main message. But in so doing we managed to anger both sides of the ideological position on the human population debate. In saying that something must be done but it can’t be done quickly, we upset the low-growth proponents. And by saying that we should nevertheless aim for long-term population reduction, we upset the people who are utterly opposed to any sort of fertility reduction or any action on human population growth.

HS: That’s something I want to ask you about — tell us about the attention this paper got within academia and in the media.

CB: Yeah, in the academic setting it was interesting. There were only a few critiques written about the paper and they were fairly weak. As the saying goes “All models are wrong but some are useful”, but what our model said was defensible. I suppose some of the terminology and the interpretation were points of contention with some people, but by and large the scientific community was satisfied with the result. But in the media it was completely different. Almost every single journalist I talked to put a particular slant on the results. Because of those two diametrically opposite opinions, people appeared to read anything they wanted to into it. Most people in the media didn’t of course read the paper. They read the title and maybe the abstract and the odd sentence here and there, and took from that whatever their ideological position dictated. There was right-wing media, there was left-wing media, and each had its own bias. I think only a handful of interviewers seemed to grasp the concept, which I didn’t think was that difficult. It also got a lot of responses on these comment streams. I don’t read those most of the time, but there are a lot of crazy people on the internet now. I got all sorts of hate mail, and even indirect death threats. Not serious ones. Just some random person telling me I should be removed from the face of the planet, and things like that. That happens from time to time when you deal with controversial topics.

HS: In the paper, you come up with some figures for what the population will be in 2100, under different scenarios. Could you tell us how much uncertainty there was around these figures?

CB: There was probably much less uncertainty than for most other species that are modelled. Humans tend to census themselves fairly well and we have a reasonable understanding of how many of us there are right now. While demographic data like age-specific survival rates are missing from some parts of the world, generally speaking at the scale of regions it’s well-known. So in terms of measurement error, the current and even the trends in those demographic rates are robust. Some of the assumptions, such as how much longer we’ll live given future medical innovations, are somewhat uncertain. But as it turns out, we are living so long now that even slight adjustments to longevity don’t make much difference in the long-term to total population size. And even large assumptions about, say, juvenile mortality, don’t make a huge difference because for a long-lived mammal the most important parameter that modifies population growth generally is the survival of breeding females. And breeding-age woman around the world tend to have the highest survival rates, so all the other parameters have smaller effects on population size. So while environmental variability has a large effect on small populations, it has a comparatively small effect on large populations. And we are a very large population. Incorporating a lot of uncertainty didn’t really make much of a difference. But the future scenarios were uncertain – will there be a war, will there be climate change reductions in food availability that will lead to higher juvenile mortality, etc.? We know little about the probability these things will occur and how important they’ll be. Read the rest of this entry »